Can the cat master a complex perceptual-cognitive task more efficiently with an intact than with a divided brain, i.e., is the capacity of a brain with united hemispheres greater than that of a brain whose hemispheres have been separated by commissurotomy? Do the differences which have been found in the brain-bisected cat's capacity for processing information in the separate hemipheres represent a general superiority in one hemisphere or an opposite superiorties of the two hemispheres foreshadowing the high degree of differential lateralization of cerebral function at the human level. Amount of functional cortex and amount of sensory input will be varied independently to deterine the relative importance of these 2 factors when bihemispherc and single-hemisphere mediation of complex problem solving are compared.